1. Introduction
The present invention generally relates to a genre of devices which detect liquid level in a container utilizing sonic wave techniques. More particularly, the present invention provides a novel liquid level detector which includes a pair of waveguides which together form axially spaced-apart pairs of discrete lenses to cross-couple refracted portions of a transmitted sonic wave pulse so as to digitalize liquid level information. Such information can then be analyzed by counting the returned cross-coupled portions which correspond to the liquid level in the container. Cross-coupling above the liquid level will, for all intents and purposes, not occur owing to the greater impedance of air. Thus, since tank geometry and the separation distance between lenses will be known values, liquid level in the container can be reliably established by counting the returned cross-coupled signals utilizing any suitable computing means.
The lenses of the present invention in their most preferred embodiment are each in the form of an inverted truncated cone having its base dimension upwardly disposed relative to the liquid surface. However, other shapes and surface curvatures are also contemplated. Thus, the lenses of the present invention in essence amount to intentional flaws in the waveguides so that discrete portions of the sonic pulses will be refracted at substantially right angles from the transmit waveguide and cross-coupled to the receive waveguide.